1. Field of the Invention
The field of this invention is the art of solidifying earth prior to the erection of a structure thereon.
2. Description of Related Art
It is known to adapt an earth auger to stir or to churn in place, rather than to excavate, a cylindrical column of earth. While the earth is being stirred in place, an earth solidifying agent, such as soil cement or cement milk, is mixed with the earth during the stirring process. The mixture of solidifying agent and earth hardens into a cylindrical shaft suitable to serve, together with a multiplicity of similar such cylindrical shafts, as a foundation for a building structure.
Since the cross section of each foundation shaft is circular and most building structures are basically rectangular, the total cross-sectional area of subjacent foundation shafts within the confines of a rectangular building structure base will be less than the cross-sectional area of the base. It has been noted that, on an average, the total cross-sectional area of cylindrical foundation shafts is approximately eighty percent of the cross-sectional area of the building structure base. As a consequence, twenty percent of the building structure is not directly supported by, or in load-bearing contact with, the foundation shafts. To compensate for this foundation bearing support differential, some builders have resorted to sinking additional foundation shafts to extend over an area wider than the building structure to be supported. This is an inefficient method of preparing a foundation.